The present invention relates to a porous hollow fiber membrane having chelate formability, as well as to a method for recovery of germanium oxide using the porous hollow fiber membrane.
Germanium is an element indispensable in various fields, for development of materials for high-technology industries such as optical fiber, solar cell and the like, or as a polymerization promotion catalyst in production of polyethylene terephthalate resin, or as a raw material for production of biologically active substance.
Recently, the supply of germanium has been unable to meet the demand and the demand and supply has become unbalanced, and this situation has been taken up as a serious problem. In Japan, the supply of germanium has been almost dependent upon import. Therefore, if the used germanium which has been entirely disposed as a waste, can be recovered by any method, it will improve the demand and supply balance of germanium and moreover is preferred from the standpoint of reutilization of resource.
Up to now, however, there has been made no proposal on any effective method for recovery of germanium, particularly germanium oxide which is used as a catalyst per se or as a raw material for germanium of various applications; and development for such an effective method has been desired.
The present invention aims at solving the above-mentioned problems of the prior art and providing a porous hollow fiber membrane capable of economically and efficiently recovering used germanium, particularly used germanium oxide heretofore disposed entirely as a waste and a method for economical and efficient recovery of germanium, particularly germanium oxide using such a porous hollow fiber membrane.
The porous hollow fiber membrane employed by the present invention in order to achieve the above aim is characterized by being obtained by reacting the residue of an epoxy group-containing compound subjected to irradiation-induced graft polymerization on a polyethylene-made porous hollow fiber membrane, with a compound capable of reacting with said reside to give a residue containing a structure represented by the following formula: 
(wherein R1 and R2 are a hydrogen atom or a lower alkyl group) or the following formula: 
The method for recovering germanium oxide using a porous hollow fiber membrane, also employed by the present invention is characterized by contacting an aqueous germanium oxide solution with the above-mentioned porous hollow fiber membrane having chelate formability, to allow the porous hollow fiber membrane having chelate formability to capture the germanium oxide contained in the aqueous solution, and then dissolving the captured germanium oxide into an acidic solution.